DescriptionHynobius nebulosus has a snout to vent length of 40-70 mm and a total length of 70-125 mm. It is a rather short-tailed, stocky salamander with 13 costal grooves and 5 toes on its hindfeet. Its limbs are also relatively short and its toes do not touch when the fore- and hindlimbs are adpressed to the flank. The overall dorsal color is light brown, liberally "misted" with tiny black dots. The ventral surface is light yellowish brown to gray. Both the dorsal and ventral edges of the tail have a bright yellow stripe which may be interrupted toward the tip of the tail. Hynobius tokyoensis is very similar and was once treated as a subspecies of H. nebulosus. However, H. tokyoensis generally has 12 costal grooves and lacks the yellow stripe on the top and underside of its tail (Goris and Maeda 2004).

Hynobius nebulosus is widely distributed west of the Suzuka Mountains of central Honshu, along the Inland Sea coast of Shikoku, in the northwestern part of Kyushu, and on Ikishima Island. It is a lowland salamander, often living in forests or talus slopes near human habitations (Goris and Maeda 2004). [3684]

Life History, Abundance, Activity, and Special Behaviors

Hynobius nebulosus belongs to the family Hynobiidae, which is one of only two salamander families exhibiting external fertilization of eggs. This species breeds in the still waters of swamps, rice paddies, and ditches. Depending on the location, rainfall, and temperature, breeding begins in December-April and continues for about 3 months. During breeding season, males grow a crest on both sides of the tail and their heads become broader. Lateral line sensory organs, which atrophy when the males are on land, once again become functional. The males arrive at the water first and stake out a territory about 20 square cm around a suitable hole, rock, bunch of leaves, etc. They defend the territory vigorously by biting, butting, and vigorous tail-waving. Males unable to establish a territory are known as "sneakers." Sneakers hover in the vicinity of a breeding couple in the hope of sneaking in and fertilizing an egg sac themselves. When a female arrives, a territorial male makes his presence known by a rhythmic series of spastic jerks. The female approaches, selects a suitable twig or other substrate, and attaches the tip of an egg sac to it. Then she lets go with all four limbs, while the male grasps her inguinal region with his forelimbs and pulls out the egg sac, squirting sperm on it as it emerges (Goris and Maeda 2004).

Two egg sacs are produced, sometimes both at the same time. There is some variation in the shape of the egg sacs, but it is usually closer to a coil than to the banana shape typical of H. tokyoensis. A total clutch consists of 50-140 eggs. At 10 degrees Celsius (50 degrees Fahrenheit), the eggs hatch in 3-4 weeks. The larvae feed on Daphina, aquatic insects, and practically anything else that moves near their snouts. Cannibalism is therefore not rare. Metamorphosis takes place in July-August and the juveniles leave the water. H. nebulosus is active only at night and, even when breeding in the paddies, remains under cover of debris or in holes, so it often goes unnoticed. It feeds on small insects, spiders, earthworms, and other small animals that frequent the forest floor. In the wild, juveniles take 2 years to reach sexual maturity and individuals live for up to 6 years. In captivity they may live 1-2 years longer (Goris and Maeda 2004).

Trends and ThreatsThe populations in Kyoto and Osaka Prefectures are threatened by housing and road construction, water pollution, invasive species and drying out of its habitat. It is also collected for the pet trade (IUCN 2006). [3719]